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2010 Pearson Education, Inc. Conceptual Physics 11 th Edition Chapter 3B: LINEAR MOTION Slide 2 2010 Pearson Education, Inc. Free Fall Falling under the influence of gravity only - with no air resistance Freely falling objects on Earth accelerate at the rate of 10 m/s/s, i.e., 10 m/s 2 (more precisely, 9.8 m/s 2 ). Slide 3 2010 Pearson Education, Inc. Free FallHow Fast? The velocity acquired by an object starting from rest is So, under free fall, when acceleration is 10 m/s 2, the speed is 10 m/s after 1 s. 20 m/s after 2 s. 30 m/s after 3 s. And so on. Slide 4 2010 Pearson Education, Inc. A free-falling object has a speed of 30 m/s at one instant. Exactly 1 s later its speed will be A.the same. B.35 m/s. C.more than 35 m/s. D.60 m/s. Free FallHow Fast? CHECK YOUR NEIGHBOR Slide 5 2010 Pearson Education, Inc. A free-falling object has a speed of 30 m/s at one instant. Exactly 1 s later its speed will be A.the same. B.35 m/s. C.more than 35 m/s. D.60 m/s. Free FallHow Fast? CHECK YOUR ANSWER Explanation: One second later its speed will be 40 m/s, which is more than 35 m/s. Slide 6 2010 Pearson Education, Inc. Free FallHow Far? The distance covered by an accelerating object starting from rest is So, under free fall, when acceleration is 10 m/s 2, the distance is 5 m/s after 1 s. 20 m/s after 2 s. 45 m/s after 3 s. And so on. Slide 7 2010 Pearson Education, Inc. What is the distance covered of a freely falling object starting from rest after 4 s? A.4 m B.16 m C.40 m D.80 m Free FallHow Far? CHECK YOUR NEIGHBOR Slide 8 2010 Pearson Education, Inc. What is the distance covered of a freely falling object starting from rest after 4 s? A.4 m B.16 m C.40 m D.80 m Free FallHow Far? CHECK YOUR ANSWER Explanation: Distance = (1/2) x acceleration x time x time So: Distance = (1/2) x 10 m/s 2 x 4 s x 4 s So:Distance = 80m